1. Field of the Invention
The present invention relates to an illumination apparatus and a projection apparatus for emitting multiple light beams of which colors are different from each other.
2. Description of the Related Art
Conventionally, at a site of a conference and the like, screen information of an information processing apparatus such as a personal computer (hereinafter abbreviated as PC) is projected onto a screen using a projector, so that information is shared by attendances at the site.
Conventionally, such projector mainly uses a high-intensity discharge lamp such as an ultrahigh pressure mercury lamp as a light source. Although the discharge lamp can achieve high luminance at a low cost, an alternative light source is required because, e.g., it takes time for the discharge lamp to emit light of a predetermined level after the discharge lamp is turned on, and because consideration is given to the environment.
Therefore, it has been proposed to use a solid-state light-emitting device such as light-emitting diodes (LEDs) of red (R), green (G), and blue (B) or an organic EL as an alternative light source in place of the discharge lamp in the projector, and such solid-state light-emitting device has been put into practice. When the solid-state light-emitting device is used as a light source of a projector, the projector can be started in a short time, and consideration can be given to the environment.
A technique to obtain lights in various colors using a blue color laser diode or a light-emitting diode emitting light of blue color, which is one of solid-state light-emitting device, has been put into practice. For example, when the blue color laser diode is used, a laser light that is output from the blue color laser diode is emitted onto a fluorescent material, so that the fluorescent material is excited, and a light in a color unique to the fluorescent material is emitted. Using these characteristics, lights of the respective colors, i.e., R, G, B, can be obtained, and a technique for using the lights obtained with the fluorescent material as a light source of the projector has been developed. Using an optical modulation device such as a DMD (Digital Micromirror Device), the lights of the respective colors, i.e., R, G, B, thus obtained are subjected to tone control for each pixel, whereby a color projection image is obtained.
For example, when the blue color laser diode is used as a light source of a projector, the amount of light is insufficient if only one laser diode is used per one color. Therefore, in general, a laser diode array, in which several to several dozen laser diodes are integrally formed as a light source, is used.
Japanese Patent Application Laid-open No. 2004-341105 discloses a projection-type display apparatus including a light-emitting diode, a fluorescent material layer converting, into a visible light, an ultraviolet light emitted by the light-emitting diode, and a transparent substrate.
According to Japanese Patent Application Laid-open No. 2004-341105, a disk is divided into three regions, and at an incident side, a visible light reflection film transmitting an ultraviolet light and reflecting a visible light is formed in each region. In each region at an emitting side opposite to the incident side with the transparent layer interposed therebetween, a fluorescent material layer for converting the wavelength of the ultraviolet light into the respective colors, i.e., R, G, B, is formed. By rotating the disk, the ultraviolet light emitted from the light source is converted into lights of wavelengths of R, G, B by each region of the fluorescent material layer, and the repeated color lights of R, G, B are emitted. The color lights are emitted onto a space optical modulator to be optically modulated, and are enlarged and projected onto a screen via a projection lens.
Furthermore, Japanese Patent Application Laid-open No. 2009-277516 discloses a light source apparatus and a projector, in which fluorescent material layers are arranged in multiple segment regions of a circular transparent substrate, and a visible light having lower level of energy than an ultraviolet light is emitted onto a fluorescent material as an excitation light, whereby lights of respective colors are obtained.
However, in the conventional techniques such as those explained in Japanese Patent Application Laid-open No. 2004-341105 and Japanese Patent Application Laid-open No. 2009-277516, the disk is divided into multiple regions by its radius, and the fluorescent material layers generating different colors in the respective divided regions are formed, so that each color is emitted in a time division manner by rotating the disk. Therefore, in the fluorescent material layer in each of the colors, the laser light is concentrated and emitted onto a limited size of area, and this makes the emitted portion into a so-called “burnt” state, which may deteriorate the characteristics of the fluorescent material layer.
In order to avoid deterioration of the characteristics of the fluorescent material layer caused by concentrated emission of the laser light onto a particular portion of each color, there is an idea to provide a disk having a fluorescent material layer for each color without dividing the disk into respective color regions. In this case, however, it is necessary to provide a light source for each color, and there is a problem in that the cost increases and the size of the apparatus increases.
Therefore, there is a need for an illumination apparatus and a projection apparatus capable of obtaining light of each color using less number of light sources in case where light of each color is obtained by exciting the fluorescent material.